1. Technical Field of the Invention
The embodiments of the invention relate to communication devices and more particularly to RF amplifiers used within such communication devices.
2. Description of Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Communication systems typically operate in accordance with one or more communication standards. For instance, wired communication systems may operate according to one or more versions of the Ethernet standard, the System Packet Interface (SPI) standard, or various other standards. Wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). Typically, the transceiver includes a data modulation stage and an RF stage. The data modulation stage (baseband process) converts between data and baseband signals in accordance with the particular wireless communication standard. The RF stage (transmitter section and receiver section) converts between baseband signals and RF signals. The RF stage may be a direct conversion transceiver that converts directly between baseband and RF or may include one or more intermediate frequency stages.
The RF stage or stages operate(s) upon RF signals, in differing channels and sub-bands of an allocated frequency band. Thus, filtering, amplifying, and signal conversion components of the RF stage operate acceptably at a variety of RF center frequencies. In many RF stages, the filtering, amplifying, and signal conversion components are tuned to operate at particular center frequencies, e.g., tuned RF circuits. By varying tuning control settings of the tuned RF circuits, the overall gain of the RF stage is optimized and power consumption is reduced. Gain boosting circuitry may be employed to control or boost gain in such RF stages.
One form of an RF stage is a differential amplifier using an inductive load, such as an inductor. Typically, it is desirable to obtain a high Q (measure of quality) for the inductor. However, because actual circuit inductors are not ideal inductors, there is a certain amount of resistance associated with the inductor. Generally, the effect of this resistance is a parallel resistance on the load of the amplifier stage, which may reduce the overall Q and/or the gain of the stage. Although active compensating circuitry may be implemented, the active component(s) may introduce noise, which may reduce the overall signal-to-noise ratio for the amplifier.
Accordingly, it would be advantageous to implement a gain boosting stage to overcome the resistance of the inductive load, in which the gain boosting is achieved with passive components.